1. Field of the Invention
The present invention relates to an anthracene derivative. Further, the present invention relates to a light-emitting element material, a light-emitting element, and an electronic appliance using the anthracene derivative.
2. Description of the Related Art
A light-emitting element using a luminescent material has features of thinness and lightweight, high response speed, low direct-current voltage drive and the like, and is expected to be applied to a next-generation flat panel display. Further, a light-emitting device in which light-emitting elements are arranged in a matrix is said to have superiority in wide viewing angle and high visibility as compared with conventional liquid crystal display devices.
A light-emitting element is said to have the following light-emission mechanism: voltage is applied between a pair of electrodes with a light-emitting layer interposed therebetween, electrons injected from a cathode and holes injected from an anode are recombined in a light-emission center of the light-emitting layer to form a molecular exciton, and then light is emitted when the molecular exciton returns to a ground state by releasing energy. An excited singlet state and an excited triplet state are known as an excited state, and it is considered that light can be emitted through either state.
An emission wavelength of a light-emitting element is determined by energy difference between a ground state and an excited state, that is, a band gap, of a light-emitting molecule included in the light-emitting element. Therefore, various emission colors can be obtained by devising structures of the light-emitting molecules. A full-color light-emitting device can be manufactured by manufacturing a light-emitting device using light-emitting elements capable of emitting light of the three primary colors of light, red, blue, and green.
In order to manufacture a full-color light-emitting device having excellent color reproducibility, red, green, and blue light-emitting elements each having high reliability and excellent color purity are required. As a result of development of materials in recent years, as for red and green light-emitting elements, high reliability and excellent color purity have been already achieved. As for a blue light-emitting element however, enough efficiency and color purity have not been achieved. For example, in Non-Patent Document 1, a blue light-emitting element with relatively high reliability is reported. For the light-emitting element, however, enough luminous efficiency and color are not realized.
[Non-Patent Document 1] J. Shi et al., Applied Physics Letters, Vol. 80, No. 17, pp. 3201-3203, 2002.